The plane wave diffraction by a slit in a material screen is analyzed using the Wiener-Hopf technique together with generalized boundary conditions (GBC). Exact and high-frequency asymptotic solutions are obtained. The scattered field is evaluated asymptotically based on the saddle point method and a far field expression is derived. Numerical examples on the far field intensity are presented and the scattering characteristics of the slit are discussed.
Very few designs are reported in the terahertz range for realizing dynamic beam-steering of the antenna radiation pattern at a fixed frequency. In this work, we propose a one-dimensional leaky-wave antenna based on nematic liquid crystals (NLC). More specifically, an NLC cell is sandwiched between two foam layers, the top one patterned with a partially reflecting sheet (PRS), and the bottom one entirely metalized to have a ground plane. Two lateral perfect magnetic conductor walls allow for a dominant TM leaky mode propagating in the structure. The beam is then steered by applying a low-frequency driving voltage through the ground and the PRS. The trade-off among radiation efficiency, angular steering range, and gain that commonly affects any reconfigurable antenna is properly handled through a suitable choice of the design parameters. Full-wave results are finally provided to demonstrate the concept.
Vehicle-to-Everything (V2X) is an emergent technology for enhancing traffic efficiency, road safety and autonomous driving. Vehicles interconnected with their prevalent wireless environment are prone to various security threats that might affect traffic and life safety immensely. Jamming attacks, a legacy and dated problem, still persists much to the havoc of V2X communications. The following paper proposes a framework for jammer detection adapted to V2X communications scenario. A Generalized Dynamic Bayesian network is used to learn the V2X signal environment in a statistical manner. Subsequently, a Modified Markov Jump Particle filter (M-MJPF) is used for signal predictions where the innovations in the observed signal versus the predicted signal enable our framework to detect the jammer. Simulation results highlight the efficacy and accuracy of our approach in V2X jammer detection.
This report presents a recently developed fabrication method combining fused deposition modelling with Field's metal for the manufacturing of complex metal structures. First, a dielectric mold is printed using standard 3D printing methods. The mold is designed with hollow cavities, which form the desired shape of the structure's metal parts. Next, molten Field's metal is injected inside, filling the cavities and adopting their architecture. Field's metal has a low melting point of 65 degrees Celsius, which can realistically be lower than the temperature where heat deformation in numerous thermoplastic materials occurs. This method can produce metamaterial resonators with high quality factors. Numerical methods are used to model the response of the metamaterial and further investigate the resonance.
The principal element of interest concerning the use of Synthetic Aperture Radar (SAR) technology in the automotive scenario is the possibility to synthesize an arbitrarily long array by exploiting the natural motion of the ego-vehicle, and therefore achieve much finer spatial resolution and improved detection capabilities without increasing hardware requirements in terms of number of physical antennas. In this paper, we discuss the application of SAR imaging in the automotive context under a theoretical and experimental perspective. Experimental results are shown based on open road campaign data acquired using an 8-channel Radar at 77 GHz, considering the cases of side-looking SAR, forward SAR, and SAR imaging of moving targets. Results corroborate the idea that SAR imaging could be successfully and systematically used in the near future for high-resolution mapping of the urban environment.
A Luneburg lens quasi-optical beam-former is used to excite a leaky-wave antenna at 275 GHz. Both the lens and the antenna are fabricated on a Cyclic Olefin Copolymer (COC) substrate. The full system is etched on the polymer by photolithography. Numerical results show a reflection coefficient lower than −24 dB and a gain higher than 21 dBi over a 40% fractional bandwidth, spanning from 220 GHz to 330 GHz. The efficiency of the antenna is estimated to be 28% at the center frequency (275 GHz).
The problem of evaluating the shielding effectiveness of a metallic circular disk with finite conductivity and finite thickness against a circular current loop coaxial with the disk is addressed. First the metallic disk is modeled through a new boundary condition which correctly takes into account the thickness of the disk and then the problem is reduced to only one set of dual integral equations which are solved in an exact form by expanding the spectral unknowns in a series of Bessel functions. The proposed formulation is compared with the one based on the Mitzner boundary conditions, showing its accuracy and the capability of reducing the computation time and with the one based on the thin-screen boundary conditions, showing that the latter can lead to erroneous results for sufficiently large thickness-to-skin-depth ratios.
An experimental setup with a solid-state microwave generator and experimental probes has been used to generate controlled ablation patterns on ex-vivo tissues. Correlation of obtained ablation patterns with microwave delivery parameters and probe types has been investigated and characterized.
In this contribution, the feasibility of a short-range ship collision avoidance system has been investigated. Based on microwave and millimeter wave radars, the system has the aim to accurately detect the presence and distance of possible obstacles inside the harbor. Indeed, whereas ships are usually equipped with long-range radars for the open-see navigation, the in-harbor navigation relies only on the manual ability of the captain. An accurate model of the real scenario is proposed by taking into account obstacles of interest like small ships and shore structures. Different operating frequencies have been considered and evaluated, thus proposing a reliable system able to effectively assist the navigation. This contribution paves the way for enabling the concept of autonomous ship navigation by exploiting advanced sensing technologies.
In this paper, we provide an overview of the stere-olithography (SLA) manufacturing process applied to the design of microwave filters. For that purpose, a spherical cavity that operates with the higher order mode TE 101 has been used in order to design filters oriented for additive manufacturing. The characteristics of such mode (high Q-factor and size) makes it an interesting choice for filters manufactured with 3-D printers. For validation purposes, two doublet prototypes with different configurations and mechanical structures have been manufactured with an SLA 3-D printer, metallized, and measured. Results show various discrepancies between the two prototypes: with measurements matching fairly well with the simulations for one prototype, while a certain frequency shift is present for the other one.
A high-gain, broadband, and low-profile Continuous Transverse Stub (CTS) antenna array is presented at Ka-band for SatCom applications. This antenna is designed to cover the downlink (17.7-20.2 GHz) and the uplink (27.5-30 GHz) bands. This array comprises 16 long slots fed in parallel by a corrugated parallel plate waveguide beam forming network. The design and simulations results are summarized, together with a simple design methodology for different network components. The dual-linear polarization is achieved by using two orthogonal modes namely: the quasi-transverse electric magnetic mode (QTEM) and the 1st order transverse electric mode (QTE1). The antenna array is well matched $(\mathrm{S}_{11} < -10\ \text{dB})$. The maximum realized gain (in one plane) is around 15 dB at 29 GHz and around 12 dB at 19 GHz for both polarizations.
Flexible interconnects are essential for power and signal transmission in wearable electronics. This paper provides a computational study of the transmission properties of interconnects fabricated on a variety of popular substrates, namely PDS, PI, PET and PU. The contributions to the reflection and transmission losses attributable to each mechanism namely, connector loss, modal loss and conductive loss, are systematically analyzed and quantified. Throughout, the study assumes realistic dielectric and conductive losses.
The present article describes the performance of a fourth-order cross-coupled bandpass filter using double-folded microstrip hairpin resonators for the improvement of skirt characteristics and harmonics suppression. The proposed filter is centered at 2.5 GHz with a fractional bandwidth of 4%. At first, the central folded pair of resonators of the unit hairpin-line cell has been modified with periodic trapezoidal corrugations to achieve improved skirt characteristics with the attenuation level of 40 dB and a compact circuit area with a size reduction of 11.36% over the conventional cross-coupled filter with the same specifications. However, the harmonics have not been suppressed significantly by this compact structure. Subsequently, trapezoidal- shaped meander spurlines have been incorporated in each coupled section of the adjacent folded hairpin-line cells for achieving modal phase velocity compensation. As a result, an extended stopband with a rejection level of 34 dB up to 3.04f0 and an overall size reduction of 20.42 % has been achieved.
A packaged transmitarray (T A) antenna operating at 77 GHz is designed. The proposed configuration is based on a standard Quad Flat No-lead package (QFN) technology. The electromagnetic field radiated by a feed placed in the QFN is focused by the transmittarray antenna placed on the package cover. An analytical model is used to estimate the basic parameters of the proposed transmit-array like gain, directivity and spillover efficiency. The final design has then been optimized through full-wave simulations. Simulated gain is 18dBi at 77Ghz while the half power beamwidth is 22°. The proposed configuration is a good candidate for automotive highly integrated mid gain applications.
An aperture coupled magneto-electric (ME) dipole for 5G Backhauling systems is proposed in this article. A substrate integrated waveguide (SIW) is used to feed the antenna. The electric dipole is formed by four identical patches, while the magnetic dipole is composed by four vertical metallic shorted vias. Moreover, a crossed strip is introduced to connect the four patches in the top metal layer to widen the impedance bandwidth and a cage of vias is added to suppress the generation of surface waves and to boost the radiating element gain. The simulated impedance bandwidth with $\vert S_{11}\vert$ < −10 dB for the proposed SIW-fed aperture coupled ME-dipole antenna fully covers the E-Band (71–86 GHz), with a fractional bandwidth of more than 20%. The simulated antenna peak gain is 10.8 dBi at 84 GHz and the 3-dB beamwidth is stable with a variation up to 1 dBi within the band of interest. The proposed E-band ME dipole antenna is very suitable for 5G backhauling systems, as it can be integrated into an array configuration for realizing beam-steering operations.
The insertion of a metamaterial (MTM) lens based on Closed Loop Resonator (CLR) into a needle microwave applicator is investigated for a more efficient hyperthermia cancer therapy. Several geometries are designed and optimized, Closed Circular-Ring Resonator (CCRR) with circular loops and Closed Square-Ring Resonator (CSRR) with square loops, with one or more concentric loops. The MTM lens is bended around to the radiating section of the antenna to form a cylindrical 3D structure. Preliminary investigations have been focused to increase the device feasibility and patient wellness. The applicator is a slot coaxial antenna inserted into a surgical needle of 16 G and operating around at the center of Industrial, Scientific, and Medical (ISM) frequency band. The experimental results pertaining to a preliminary fabricated prototype of needle applicator are encouraging, and the simulation results suggest that they could be improved by using the investigated MTM lens.
This paper presents a design of a superdirective array of 3 monopoles antennas with radiation pattern reconfigurable for Wi-Fi box in ISM band. It is principally based on Uzkov's theory, who define the possibility to obtain a high directivity in order of N 2 in a desired direction by linearly associating a large number of N radiators closely spaced. Since we calculated specific currents excitation in magnitude and phase to obtain a superdirectivity reconfigurable for desired direction, we design this array antennas by exciting one monopole by a unit current and loaded the others two by impedances Znload determined from uzkov's theory. This impedances are each other directly connected to its pin diode which allow to swicth in a desired direction without any mutual coupling between monopoles and cover all 360 deg of azimutal plane. This array antennas, efficient at 96%, presents approximately similar results in all 360 deg of azimtal plane with a reconfigurable directivity in order of 5.2dB and a Back lobe of −14dB with an Half Power Beam of around 120 deg in every direction.
This paper demonstrates the importance of a mesh used for describing a rectangular patch antenna bent over a cylinder and its effect on results and their nature. Advantages of the cylindrical TLM mesh, as the perfectly aligned mesh to the considered structure, are emphasized over the rectangular TLM mesh that requires much finer mesh to be used due to inevitable numerical error introduced by approximations leading to lower efficiency.
Multipactor is nowadays crucial when analyzing the final performance of satellite communication systems, as the critical components of these systems must meet demanding high-power specifications. Therefore, having access to fast and reliable multipactor simulations is of paramount importance for the radio frequency (RF) design process. This paper describes the Coarse method as a technique enabling faster predictions for time-varying signals, but also highlights the limitations of the method when analyzing long signals. In this work, the capabilities of the Coarse method are expanded by introducing the Kadane's search algorithm, which allows to identify the multipactor critical sequence of long signals with a limited CPU effort.
